Method and apparatus for changing the perspective view of a three-dimensional object image displayed on a display screen

Abstract

An apparatus and method for rotating a perspective view of a three-dimensional object image displayed on a display screen from an original view point to a desired view point, and for moving the perspective view in a parallel manner from the original view point to the desired view point. When the perspective view is rotated, a circle is generated that has a first point corresponding to the desired view point. A line segment is generated from the first point to the center of the circle. A hemisphere is generated that has a top surface, a vertex, and the circle as a bottom surface. A second point on the top surface represents the first point projected to the top surface. The desired view point is a projection from the second point to the bottom surface of the hemisphere and the original view point is a projection from the vertex of the hemisphere. The perspective view displayed on the display screen is then changed to the desired view point. When the perspective view is moved in a parallel manner, a boundary is generated which represents a displayable range of the three-dimensional object image on the display screen. A line segment is generated from the current cursor position to the center of the boundary. The displayed perspective view is changed by moving the perspective view along the line segment by a distance equal to the length of the line segment.

I claim: 
     
       1. A method for rotating a perspective view of a three-dimensional object image displayed on a two-dimensional display screen, the perspective view of the three-dimensional object image being rotated from an original view point to a desired view point and a cursor indicating the desired view point on the display screen, the method comprising the steps of: instructing a rotation of the perspective view of the three-dimensional object image from the original view point to the desired view point, by moving the cursor to the desired view point on the display screen;   displaying a circle on the display screen, the circle overlapping the three-dimensional object image displayed on the display screen, the desired view point corresponding to a first point in the area of the circle;   displaying a line segment on the display screen, the line segment directed from the first point in the area of the circle to the center of the circle;   generating a hemisphere having a top surface and a circular bottom surface, the circumference of the bottom surface being the circle, where a second point on the top surface of the hemisphere represents the first point projected to the top surface of the hemisphere, the desired view point is a projection from the second point to the bottom surface of the hemisphere and the original view point is a projection from the vertex of the hemisphere; and   rotating the perspective view of the three-dimensional object image by changing the view point from the original view point to the desired view point.   
     
     
       2. A method as claimed in claim 1, wherein: the step of generating a hemisphere comprises calculating a rotation angle and a rotation direction to move the desired view point to the vertex of the hemisphere; and   the step of rotating the perspective view of the three-dimensional object image comprises rotating the perspective view of the three-dimensional object image by the rotation angle in the rotation direction.   
     
     
       3. A method as claimed in claim 2, wherein the step of displaying a circle and the step of displaying a line segment generate image data in response to an instruction to rotate the perspective view of the three-dimensional object image, the image data including circle data relating to the circle and directional segment data relating to the line segment, the method further comprising storing the image data. 
     
     
       4. A method as claimed in claim 3, wherein the method allows for either a parallel movement of the perspective view of the three-dimensional object image or a rotation of the perspective view of the three-dimensional object image, and the steps of displaying a circle, displaying a line segment, generating a hemisphere and rotating the perspective view of the three-dimensional object image are performed only when a rotation is instructed and wherein the method uses a mouse comprising a first switch to input a position of the cursor and to move the cursor, a second switch to instruct a parallel movement of the perspective view of the three-dimensional object image displayed on the display screen, and a third switch to instruct a rotation of the perspective view of the three-dimensional object image displayed on the display screen, wherein the step of instructing a rotation uses the mouse to input a position of the cursor, to move the cursor and to instruct a rotation of the perspective view of the three-dimensional object image, the method further comprising a step of instructing a parallel movement of the perspective view of the three-dimensional object image which uses the mouse to input a position of the cursor, to move the cursor and to instruct a parallel movement of the perspective view of the three-dimensional object image. 
     
     
       5. A method as claimed in claim 4, wherein the step of instructing a rotation comprises, when the third switch is operated, instructing a rotation of the perspective view of the three-dimensional object image and the step of instructing a parallel movement comprises, when the second switch is operated, instructing a parallel movement of the perspective view of the three-dimensional object image. 
     
     
       6. A method as claimed in claim 5, further comprising, when the second switch is operated to instruct a parallel movement of the perspective view of the three-dimensional object: generating a boundary representing a range of the three-dimensional object image displayable on the display screen, where the cursor position when the second switch is operated is the center of the range;   displaying a line segment directed from the center of the range to the center of the display screen; and   moving the perspective view of the three-dimensional object image along the line segment by the distance equal to the length of the line segment.   
     
     
       7. A method as claimed in claim 6, wherein the step of instructing a rotation comprises instructing a rotation by pressing the third switch, and the step of rotating the perspective view of the three-dimensional object image comprises displaying, when the third switch is released, the rotated perspective view of the three-dimensional object image. 
     
     
       8. A method as claimed in claim 6, wherein the step of instructing a parallel movement of the perspective view of the three-dimensional object image comprises instructing a parallel movement by pressing the second switch, the method further comprising: displaying, when the second switch is released, the moved perspective view of the three-dimensional object image.   
     
     
       9. A method for displaying a perspective view of a three-dimensional object image on a display screen, the perspective view of the three-dimensional object image being rotated from an original view point to a desired view point and a cursor indicating a position on the display screen, the method comprising the steps of: instructing a rotation of the perspective view of the three-dimensional image from the original view point to the desired view point on the display screen;   displaying a circle on the display screen, the circle overlapping the three-dimensional object image, the circle having a radius which allows the entire circle to be displayed on the display screen, the desired view point corresponding to a first point in the area of the circle;   displaying a line segment on the display screen, the line segment directed from the first point to the center of the circle;   changing the direction, the length, and the displayable range of the line segment in accordance with the movement of the cursor;   generating a hemisphere having a top surface and a circular bottom surface, the circumference of the bottom surface being the circle, where a second point on the top surface of the hemisphere represents the first point projected to the top surface of the hemisphere, the desired view point is a projection from the second point to the bottom surface of the hemisphere and the original view point is a projection from the vertex of the hemisphere; and   displaying a perspective view of the three-dimensional object image on the display screen, as viewed from the desired view point.   
     
     
       10. A method as claimed in claim 9, further comprising the steps of: determining a rotation angle between the desired view point and the vertex of the hemisphere; and   determining a rotation direction to move the desired view point to the vertex of the hemisphere;   wherein the step of displaying a perspective view of the three-dimensional object image comprises rotating the perspective view of the three-dimensional object image by the rotation angle in the rotation direction.   
     
     
       11. A method as claimed in claim 10, wherein the method allows for either a rotation of the perspective view of the three-dimensional object image or a parallel movement of the perspective view of the three-dimensional object image, the perspective view of the three-dimensional object image being moved from the original view point to the desired view point when a parallel movement is instructed, the steps of displaying a circle, displaying a line segment, changing the direction, generating a hemisphere and displaying the perspective view of the three-dimensional object image are performed only when a rotation is instructed, further comprising the step of instructing a parallel movement of the perspective view of the three-dimensional image from the original view point to the desired view point on the display screen and, when a parallel movement is instructed, the following steps are performed: displaying a boundary representing a range of the three-dimensional object image displayable on the display screen, where the position indicated by the cursor is the center of the range;   displaying a line segment directed from the current cursor position to the center of the range;   changing the direction and length of the line segment in accordance with movement of the cursor; and   moving the perspective view of the three-dimensional object image on the display screen by moving the current position indicated by the cursor to the center of the display screen.   
     
     
       12. A method as claimed in claim 11, wherein the method uses a mouse comprising a first switch to input a position of the cursor and to move the cursor, a second switch to instruct a parallel movement of the perspective view of the three-dimensional object image displayed on the display screen, and a third switch to instruct a rotation of the perspective view of the three-dimensional object image displayed on the display screen, wherein the step of instructing a rotation uses the mouse to instruct a rotation and the step of instructing a parallel movement uses the mouse to instruct a parallel movement. 
     
     
       13. A method as claimed in claim 12, wherein the step of instructing a rotation comprises, when the third switch is operated, instructing a rotation of the perspective view of the three-dimensional object image; and   the step of instructing a parallel movement comprises, when the second switch is operated, instructing a parallel movement of the perspective view of the three-dimensional object image.   
     
     
       14. A method as claimed in claim 13, wherein the step of instructing a rotation comprises instructing a rotation by pressing the third switch, and the step of displaying perspective view of the three-dimensional object image, when an instruction of rotation is made, comprises displaying the perspective view of the three-dimensional object image when the third switch is released. 
     
     
       15. A method as claimed in claim 13, wherein the step of instructing a parallel movement comprises instructing a parallel movement by pressing the second switch, and the step of moving the perspective view of the three-dimensional object image comprises moving the perspective view of the three-dimensional object image when the second switch is released. 
     
     
       16. An apparatus for rotating a perspective view of a three-dimensional object image displayed on a two-dimensional display screen, the perspective view being rotated from an original view point to a desired view point, the apparatus comprising: display means, comprising a two-dimensional display screen and a cursor which indicates the desired view point on the display screen, for displaying a perspective view of the three-dimensional object image corresponding to the original view point on the display screen;   instructing means for instructing the apparatus, by moving the cursor to the desired view point on the display screen, to rotate the perspective view of the three-dimensional object image from the original view point to the desired view point;   circle data generating means for determining, when an instruction to rotate the perspective view of the three-dimensional object image is made by the instructing means, a circle that overlaps the three-dimensional object image displayed on the display screen, the desired view point corresponding to a first point in the area of the circle, and for generating circle data which represents the circle, the display means displaying the circle represented by the circle data on the display screen;   directional segment data generating means for determining, when an instruction to rotate the perspective view of the three-dimensional object image is made by the instructing means, a line segment directed from the first point in the area of the circle to the center of the circle, and for generating direction segment data which represents the line segment, the display means displaying the line segment represented by the direction segment data by overlapping the line segment with the circle and the three-dimensional object image;   hemisphere data generating means for determining, when an instruction to rotate the perspective view of the three-dimensional object image is made by the instructing means, a hemisphere having a top surface, a vertex on the top surface and a circular bottom surface, the circumference of the bottom surface being the circle, and for generating hemisphere data representing the hemisphere, where a second point on the top surface of the hemisphere represents the first point in the area of the circle being projected to the top surface of the hemisphere, the desired view point is a projection from the second point to the bottom surface of the hemisphere and the original view point is a projection from the vertex of the hemisphere; and   display control means for rotating the perspective view of the three-dimensional object image on the display screen by changing the view point from the original view point to the desired view point.   
     
     
       17. An apparatus as claimed in claim 16, wherein the hemisphere data generating means comprises angle and direction calculating means for calculating a rotation angle and a rotation direction to move the desired view point to the vertex of the hemisphere, the display control means rotating the perspective view of the three-dimensional object image by the rotation angle in the rotation direction. 
     
     
       18. An apparatus as claimed in claim 17, wherein the circle data generating means and the directional segment data generating means together represent a panning control means for generating image data in response to an instruction from the instructing means to rotate the perspective view of the three-dimensional object image, the image data including the circle data and the directional segment data, the apparatus further comprising: image data storing means for storing the image data, the display means displaying the circle and the line segment based on the image data stored in the image data storing means.   
     
     
       19. An apparatus as claimed in claim 18, the apparatus allowing for either a parallel movement or the perspective view of the three-dimensional object image or a rotation of the perspective view of the three-dimensional object image, wherein the instructing means comprises a mouse, the mouse comprising: a first switch to input a position of the cursor into the panning control means and to move the cursor;   a second switch to instruct a parallel movement of the perspective view of the three-dimensional object image displayed on the display screen; and   a third switch to instruct a rotation of the perspective view of the three-dimensional object image displayed on the display screen.   
     
     
       20. An apparatus as claimed in claim 19, wherein, when the third switch is operated, an instruction to rotate the perspective view of the three-dimensional object image is sent to the panning control means and, when the second switch is operated, the apparatus is instructed to perform a parallel movement of the perspective view of the three-dimensional object image. 
     
     
       21. An apparatus as claimed in claim 20, further comprising boundary line data generating means for generating, when the second switch is operated to instruct a parallel movement of the perspective view of the three-dimensional object image, a boundary representing a range of the three-dimensional object image displayable on the display screen, where the cursor position when the second switch is operated is the center of the range, the directional segment data generating means determining a line segment directed from the center of the range to the center of the display screen and the display control means moving the perspective view of the three-dimensional object image along the line segment by a distance equal to the length of the line segment. 
     
     
       22. An apparatus as claimed in claim 6, wherein a rotation of the perspective view of the three-dimensional object is instructed by pressing the third switch, and the rotated perspective view of the three-dimensional object is displayed by releasing the third switch. 
     
     
       23. An apparatus as claimed in claim 21, wherein a parallel movement of the perspective view of the three-dimensional object is instructed by pressing the second switch, and the moved perspective view of the three-dimensional object is displayed by releasing the second switch.